Re: [Qemu-devel] [kvm-unit-tests PATCH v11 1/3] arm: Add PMU test

[Andre Przywara]

Hi,

On 22/11/16 18:29, Wei Huang wrote:
> From: Christopher Covington <address@hidden>
> 
> Beginning with a simple sanity check of the control register, add
> a unit test for the ARM Performance Monitors Unit (PMU).

Mmh, the output of this is a bit confusing. How about to join some
information? I changed it to give me:
INFO: pmu: PMU implementer/ID code:     "A"(0x41)/0x0
INFO: pmu: Event counters:      0
PASS: pmu: Control register

... by using the newly introduced report_info() to make it look nicer.

> 
> Signed-off-by: Christopher Covington <address@hidden>
> Signed-off-by: Wei Huang <address@hidden>
> Reviewed-by: Andrew Jones <address@hidden>
> ---
>  arm/Makefile.common |  3 ++-
>  arm/pmu.c           | 74 
> +++++++++++++++++++++++++++++++++++++++++++++++++++++
>  arm/unittests.cfg   |  5 ++++
>  3 files changed, 81 insertions(+), 1 deletion(-)
>  create mode 100644 arm/pmu.c
> 
> diff --git a/arm/Makefile.common b/arm/Makefile.common
> index f37b5c2..5da2fdd 100644
> --- a/arm/Makefile.common
> +++ b/arm/Makefile.common
> @@ -12,7 +12,8 @@ endif
>  tests-common = \
>       $(TEST_DIR)/selftest.flat \
>       $(TEST_DIR)/spinlock-test.flat \
> -     $(TEST_DIR)/pci-test.flat
> +     $(TEST_DIR)/pci-test.flat \
> +     $(TEST_DIR)/pmu.flat
>  
>  all: test_cases
>  
> diff --git a/arm/pmu.c b/arm/pmu.c
> new file mode 100644
> index 0000000..9d9c53b
> --- /dev/null
> +++ b/arm/pmu.c
> @@ -0,0 +1,74 @@
> +/*
> + * Test the ARM Performance Monitors Unit (PMU).
> + *
> + * Copyright (c) 2015-2016, The Linux Foundation. All rights reserved.
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms of the GNU Lesser General Public License version 2.1 and
> + * only version 2.1 as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful, but 
> WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public 
> License
> + * for more details.
> + */
> +#include "libcflat.h"
> +#include "asm/barrier.h"
> +
> +#define PMU_PMCR_N_SHIFT   11
> +#define PMU_PMCR_N_MASK    0x1f
> +#define PMU_PMCR_ID_SHIFT  16
> +#define PMU_PMCR_ID_MASK   0xff
> +#define PMU_PMCR_IMP_SHIFT 24
> +#define PMU_PMCR_IMP_MASK  0xff
> +
> +#if defined(__arm__)

I guess you should use the arch specific header files we have in place
for that (lib/arm{.64}/asm/processor.h). Also there are sysreg read
wrappers (at least for arm64) in there already, can't we base this
function on them: DEFINE_GET_SYSREG32(pmcr, el0)?
(Requires a small change to get rid of the forced "_el1" suffix)

We should wait for the GIC series to be merged, as this contains some
changes in this area.

> +static inline uint32_t pmcr_read(void)
> +{
> +     uint32_t ret;
> +
> +     asm volatile("mrc p15, 0, %0, c9, c12, 0" : "=r" (ret));
> +     return ret;
> +}
> +#elif defined(__aarch64__)
> +static inline uint32_t pmcr_read(void)
> +{
> +     uint32_t ret;
> +
> +     asm volatile("mrs %0, pmcr_el0" : "=r" (ret));
> +     return ret;
> +}
> +#endif
> +
> +/*
> + * As a simple sanity check on the PMCR_EL0, ensure the implementer field 
> isn't
> + * null. Also print out a couple other interesting fields for diagnostic
> + * purposes. For example, as of fall 2016, QEMU TCG mode doesn't implement
> + * event counters and therefore reports zero event counters, but hopefully
> + * support for at least the instructions event will be added in the future 
> and
> + * the reported number of event counters will become nonzero.
> + */
> +static bool check_pmcr(void)
> +{
> +     uint32_t pmcr;
> +
> +     pmcr = pmcr_read();
> +
> +     printf("PMU implementer:     %c\n",
> +            (pmcr >> PMU_PMCR_IMP_SHIFT) & PMU_PMCR_IMP_MASK);

If this register reads as zero, the output is mangled (since it cuts off
the string before the newline):
=====
PMU implementer:     Identification code: 0x0
=====

I guess you need something like:
(pmcr >> PMU_PMCR_IMP_SHIFT) & PMU_PMCR_IMP_MASK ?: ' '

> +     printf("Identification code: 0x%x\n",
> +            (pmcr >> PMU_PMCR_ID_SHIFT) & PMU_PMCR_ID_MASK);

As mentioned above this should use report_info() now, also it would be
nice to merge this with the message above into one line of output.

Cheers,
Andre

> +     printf("Event counters:      %d\n",
> +            (pmcr >> PMU_PMCR_N_SHIFT) & PMU_PMCR_N_MASK);
> +
> +     return ((pmcr >> PMU_PMCR_IMP_SHIFT) & PMU_PMCR_IMP_MASK) != 0;
> +}
> +
> +int main(void)
> +{
> +     report_prefix_push("pmu");
> +
> +     report("Control register", check_pmcr());
> +
> +     return report_summary();
> +}
> diff --git a/arm/unittests.cfg b/arm/unittests.cfg
> index ae32a42..816f494 100644
> --- a/arm/unittests.cfg
> +++ b/arm/unittests.cfg
> @@ -58,3 +58,8 @@ groups = selftest
>  [pci-test]
>  file = pci-test.flat
>  groups = pci
> +
> +# Test PMU support
> +[pmu]
> +file = pmu.flat
> +groups = pmu
>